Natural History ~ In Brief
It is a great lake!
Lake Champlain is the sixth largest body of fresh water in the United States, topped in size only by the five Great Lakes. Champlain covers 435 square miles of surface water and contains more than 70 islands. The lake is 120 miles long with nearly 600 miles of shoreline and lies in a valley flanked by Vermont’s Green Mountains to the east and New York’s Adirondacks to the west. Lake Champlain contains 6.8 trillion gallons of water and is a drinking water source for nearly 200,000 people.
The lake has five major segments: the South Lake, long skinny and riverine; the Main Lake, the deepest and widest section; Malletts Bay, circumscribed by historical railroad and road causeways; the Inland Sea, which lies to the east of the Hero Islands; and Missisquoi Bay, a large and discrete bay rich with wildlife.
Thirty-one major tributaries drain the 8,234 square mile Lake Champlain Basin, delivering over 91 percent of the water entering the lake. The deltaic mouths and associated wetlands of these tributaries provide some of the most interesting paddling opportunities on the lake.
The rocks and landforms of the Lake Champlain valley are a geologist’s dream. The oldest fossil coral reef in the world, young mountains made of ancient rocks, and the excavation site of a 10,000 year-old beluga whale are just three examples of the lake’s many geologic delights.
The New York shoreline from the vicinity of Port Kent south is “basement” rock, part of an ancient range of mountains that pre-dated the Adirondacks. Thought the Adirondack Mountains themselves formed a mere 20 million years ago, these rocks are over one billion years old!
The New York shoreline at the northern end of the lake and nearly all of the Vermont shoreline is composed of sedimentary rocks (limestones, dolostones, quartzites) which were deposited in a shallow tropical sea about 500 million years ago. The fossilized coral reefs on Isle La Motte formed during this period, as did fossils at Button Bay.
The precursor to Lake Champlain formed about 200 million years ago. At that time the stretching of continents caused a massive piece of bedrock to fall down between two parallel faults forming a deep canyon known as a graben valley.
More recently, the Pleistocene glaciers overrode the area as far south as Long Island, blanketing the area in a mile thick sheet of ice. The glaciers moved laterally over the landscape as they grew thicker, following the paths of least resistance through valleys. Along the way rocks and boulders dragged beneath the ice sheet acted like sandpaper rubbed against the land. Glaciation started about three million years ago and continued to about 12,000 years ago.
As the ice began to melt, the slowly retreating glaciers to the north limited the flow of the meltwater forcing drainage to the south through the present day Hudson River. Debris dams forced the water to pool in a huge lake – Lake Vermont. At its height, Lake Vermont had a surface elevation around 500 feet higher than Lake Champlain’s current level!
When the glacier receded north of the St. Lawrence Valley, the landmass it had covered was below sea level as a result of the huge weight of the ice. Ocean waters flowed in from the Atlantic forming the Champlain Sea. Saltwater animals such as the famous Charlotte whale frolicked in the region at that time. Subsequent rebounding of the land raised the lake elevation above sea level. Gradually saltwater flushed out and was replaced by fresh water from tributaries.
Lake Champlain can be divided into four distinct zones. Nearshore is the littoral zone. This is the area where sunlight penetrates to the bottom of the lake and submerged vegetation can grow. With the invasion of zebra mussels, the littoral zone has grown in some areas because zebra mussels filter feed and can increase water clarity. Deeper waters can be divided into a limnetic zone and a profundal zone. The limnetic zone is the open water area where sunlight can penetrate, but not to the bottom. Here algae dominate the base of the food chain. The perpetually dark profundal zone sits beneath the limnetic zone, beyond the reach of sunlight. Underneath it all is the benthic zone, the sediment layer which provides a home for many organisms. They find their sustenance from the detritus that sinks to the bottom through the year.
Wetlands, the transition zone between land and water, are defined by their soil type, the amount of standing water they hold in a year, and their vegetation. Lake Champlain’s wetland communities include marshes, lakeshore grasslands, lakeside floodplain forests, and riverine floodplain forests. Many of the lake’s shoreline wetlands have been created over thousands of years by fluctuating Lake levels. A 1994 Lake Champlain Basin Program study identified 166 major wetlands, at least 50 acres or larger, with a direct hydrological connection to Lake Champlain.
Wetlands improve water quality by filtering sediments, pollutants and nutrients. They protect groundwater and drinking water supplies, control flooding, stabilize shorelines and prevent erosion. They provide havens for numerous fish and wildlife: pike spawn in flooded fields, amphibians breed in temporary pools, and numerous bird species depend on the cover provided by cattails.
Many wetlands have been lost to development pressure in recent decades. Strong regulations and strict enforcement are necessary to protect those that remain.
Some distinctive shoreline vegetation communities can be found around Lake Champlain. Cobble beaches occur regularly where constant disturbances from waves fragment rocks, and prevent permanent establishment of vegetation. Natural sand beaches and dunes are found in only a few locations where rivers deposit their sediments or where currents wash eroded sands into the base of some bays. Dunes form along the landside of some of the larger beaches, when blowing winds pile the sand into cliffs and hills. White cedar communities perch atop many limestone and dolomite cliffs along the lake.
The book Wetland, Woodland, Wildland offers more detailed information about natural communities of the lake and surrounding uplands.
Lake Champlain provides a rich environment for a multitude of animal species.
Most visible are the birds that fly and hunt over the water. Over 250 species can be found within the Lake Champlain Basin in a given year. Four species of gulls are regularly seen on the lake. Most common and familiar are the ubiquitous ring-billed gulls and the larger herring gulls. A few massive great black-backed gulls can be seen year round, while small dainty tern-like Bonaparte's gulls are seen most frequently in the spring and fall. Double-crested cormorants hunt throughout the lake during the summer; this now common species was first reported nesting on the lake in the early 1980s. Bald eagles and osprey soar about. Common and Caspian terns breed on islands. Wading birds that stalk the shorelines and weedy areas include great blue herons, green herons, American bitterns, black-crowned night herons, and, more recently, great egrets. The most frequently sighted duck species are common mergansers, a diving duck, and mallards and wood ducks, both puddle ducks. During the winter, large rafts of common goldeneye float on calm water.
Fish attract anglers from throughout the country. Lake Champlain hosts about seventy species of fish and another dozen or so species inhabit tributaries between the lake and the fall line. Popular game species include an abundance of different panfish, smallmouth and largemouth bass, northern pike, lake trout, and Atlantic salmon.
Most of the creatures that live in the lake are invertebrates - insects, snails, mussels, worms, a variety of zooplankton, and more. Invertebrate communities are little thought of and not well understood, but they are an integral part of Lake Champlain's ecosystem.